Adjustable Rate Mortgages (ARM)

Adjustable Rate Mortgages (ARM)s are loans whose interest rate can vary during the loan's term. These loans usually have a fixed interest rate for an initial period of time and then can adjust based on current market conditions. The initial rate on an ARM is potentially lower than on a fixed rate mortgage, which allows you to afford and hence purchase a more expensive home. Adjustable rate mortgages are usually amortized over a period of 30 years with the initial rate being fixed for anywhere from 1 month to 10 years. 

When the time comes for the ARM to adjust, the rate will adjust to wherever the markets are at that point, based on a variety of factors such as the margin and index. That rate will then be fixed for the next adjustment period. This adjustment can occur every year, but there are factors limiting how much the rates can adjust. These factors are called "caps". Suppose you had a "3/1 ARM" with an initial cap of 2%, a lifetime cap of 6%, and initial interest rate of 6.25%. The highest rate you could have in the fourth year would be 8.25%, and the highest rate you could have during the life of the loan would be 12.25%.